1. Field of the Invention
The present invention relates to the field of LED (Light-Emitting Diode) encapsulation technology, and in particular to and LED encapsulation comprising a quantum device and a manufacturing method thereof.
2. The Related Arts
A quantum dot (QD), which is also referred to as a nanocrysal, is formed of a limited number of atoms and has three dimensional sizes all in the order of nanometers. Referring to FIG. 1, the quantum dot is generally in the form of sphere or a sphere-like shape and is a nanometer particle made of a semiconductor material (commonly composed of groups II-VI or group III-V elements) and having a stable diameter between 1-10 nm. The quantum dot is a nanometer scale aggregate of atoms and molecules and can be formed of one kind of semiconductor material, such as composed of elements of groups II and VI (for example CdS, CdSe, CdTe, ZnSe, and the likes) or elements of groups III and V (for example InP, InAs, and the likes), or can alternatively be composed to two kinds or more than two kinds of semiconductor materials.
The quantum dot is a semiconducting nanometer structure that confines conduction band electrons, valence band holes, and excitons in three spatial directions. Since the conduction band electrons and the valence band holes are subjected to quantum confinement, the continuous energy band converts into spilt energy levels having molecular characteristics and fluorescence occurs upon excitement. Due to the quantum effect, the quantum dot has a prosperous future of wide applications in various fields, such as solar cells, light emission devices, and optic bio-marking.
The photo-electronic characteristics of a quantum dot are closely related to the size and shape thereof. Researches reveal that the band gap of a quantum dot is inversely proportional to the size. In other words, the smaller the size of a quantum dot is, the wider the band gap will be, making an emitting light shifted toward blue. Thus, controlling the sizes of quantum dots allows for production of quantum dots that give of different spectra of light emission. The intensity of a light emission spectrum of a quantum dot is illustrated in FIG. 2. It can be seen from the drawing that the half-peak width (around 50-60 nm) of a quantum dot is narrower than those of the green (having a half-peak width of 80 nm) and red (having a half-peak width of 100 nm) fluorescent powders commonly used in the conventional LED lights. For television applications, it can be well used in combination with photoresist (color filter (CF)) to exhibit high transmittance while ensuring high color gamut.
Heretofore, the commercial quantum dot materials generally comprise a core made of cadmium selenide (CdSe) and a shell made of cadmium sulfide (CdS). The quantum dot material may get failure when affected by high temperatures and oxygen. Thus, currently, the commercial uses of quantum dots require protections of the quantum dot material. The protection of the quantum dot material can be realized through two ways, of which one is made in the form of a quantum dot film (QD film) having a structure illustrated in FIG. 3, in which polyethylene terephthalate (PET) material 104 is used to encapsulate a quantum dot material 102, a moisture barrier layer 106 and an LED encapsulant 108 being also shown in the drawing; and another way is made in the form of a quantum dot rail (QD rail) having a structure illustrated in FIG. 4, in which a hollow glass tube 202 is used to encapsulate a quantum dot material 102.
The QD film uses more quantum dot material and is hard to control chromaticity in a back light unit (BLU) and has a poor mass-productivity. On the other hand, the QD rail has a better mass-productivity in respect of price and chromaticity control. In the applications of side edge backlight modules, a QD rail and an LED element 304 are positioned and assembled as illustrated in FIGS. 5 and 6, where the LED element 304 is mounted in a mixing cup 308 arranged on a PCB (Printed Circuit Board) 306 and is electrically connected to the PCB 306. The mixing cup has a light exit surface and the QD rail 302 is positioned on the light exit surface. A flow of assembling the QD rail 302 and the LED element 304 is illustrated in FIG. 7, where the assembly of the QD rail 302 and the LED element 304 includes three steps: Firstly, the LED element 304 is mounted on the PCB 306 and the LED 304 is also electrically connected to the PCB 306; secondly, a mixing cup 307 is formed on the PCB 306; and thirdly, the QD rail 302 is mounted on a light exit surface of the mixing cup 308. To ensure the utilization of the QD rail 302 and to suppress light leaking, the combination of the QD rail 302 and the LED element 304 must maintain perfect aligning. Further, the combination of the mixing cup 308 and the QD rail 302 must also maintain excellent stability to avoid the occurrence of shaking and detachment. Since the glass tube of the QD rail 302 is fragile, the assembling process faces great challenges and risks.